1. Field of the Invention
The present invention relates to an optical apparatus for observing, with a pair of right and left ocular optical systems (eyepieces), images formed by a pair of right and left objective optical systems (objective lenses), and more particularly to an optical apparatus such as a binocular arranged to correct shaking of the observed images during the holding of the optical apparatus by correctively shifting on a focal plane the images formed by the pair of right and left objective optical systems.
2. Description of Related Art
Heretofore, there have been proposed binoculars of the kind arranged to be capable of correcting shaking of observed images caused by the vibration of holding hands, for example, as follows.
(i) Prism binoculars each arranged to correct shaking of observed images during the holding of the binocular by correctively rotating the whole or a part of an erecting optical system including a prism, a mirror or the like with respect to a fixed body part of the binocular in such a way as to shift focusing images (Japanese Laid-Open Patent Applications No. SHO 54-23554 and No. HEI 2-284113). PA1 (ii) A binocular in which a prism having a vertical-angle varying function is disposed closer to the object than the focal plane of each of objective lenses of the right and left lens barrels rotatably interconnected to each other, and the angle of reflection or the angle of refraction in such a prism is correctively varied so as to correct shaking of observed images during the holding of the binocular (Japanese Laid-Open Patent Application No. HEI 7-84223).
Of the binoculars having the erecting optical system correctively rotated as mentioned in Paragraph (i) above, the binocular proposed in Japanese Laid-Open Patent Application No. SHO 54-23554 is arranged to integrally swing a pair of right and left prisms serving as the erecting optical system with respect to the fixed body part of the binocular. This arrangement, therefore, necessitates a large structure for supporting the prisms and is thus hardly suited for a compact binocular. Further, the binocular proposed in Japanese Laid-Open Patent Application No. HEI 2-284113 is arranged to use a part of a mirror serving as the erecting optical system in common for the right and left systems and to drive and decenter the part of the mirror. This arrangement has an advantage in that a pair of light fluxes passing through a pair of objective optical systems can be simultaneously deflected and controlled, but has a shortcoming in that there is required a prism exclusively used for adjustment of an interpupillary distance. Further, both of these binoculars necessitate inclusion of erecting optical systems such as prisms as indispensable components and, therefore, the arrangements of them cannot be applied to some binoculars having no erecting optical system, such as a Galilean binocular.
On the other hand, the binocular proposed in Japanese Laid-Open Patent Application No. HEI 7-84223 necessitates addition of a separate optical part (a prism having the vertical-angle varying function) for shifting a focusing image by bending the optical axis to each of the right and left optical systems constituting the binocular. The additional optical part has presented a problem in respect of cost and size. Besides, since the right and left lens barrels are rotatably interconnected, it is necessary to pay attention to the adjustment of right and left optical axes.